Every February our phone fills with the same call: icicles along the gutters and water coming in over the front door. That's an ice dam, and here's the thing most roofers won't tell you — the cause is almost never the roof or the gutter. It's warm air leaking into the attic. We stop the leak fast and then fix the actual cause so you're not calling again next winter.
How ice dams form
Snow falls on the roof. Warm air leaking from the house into the attic heats the underside of the deck, melting the snow on the upper roof. That meltwater runs down to the cold eave — which isn't heated by attic air — and refreezes into a ridge of ice. The next round of meltwater pools behind that ridge, backs up under the shingles, and runs into the wall or ceiling. The icicles you see are the symptom; the warm attic is the disease.
Stopping an active dam — safely
If water is coming in right now, the safe removal method is low-pressure steam, which melts channels through the ice without harming the shingles. We coordinate steam removal quickly. What we will not do — and what you should never let anyone do — is chip the ice off with hammers, picks, or shovels, or run a torch on the roof. That destroys shingles and creates a bigger leak. Heated cables are a band-aid too: they channel some water but don't address the cause, and dams just form above them.
The permanent fix is in the attic
- Air-seal the attic floor — every gap where warm air leaks up (top plates, recessed lights, bath-fan ducts, dropped soffits) gets sealed. This is the single most effective fix.
- Add insulation — R-49 (about 14 inches) is the modern NJ target. Most pre-1990 homes have R-19 to R-30. More insulation keeps the attic cold so the deck stays cold so the snow doesn't melt early.
- Balance ventilation — continuous ridge vent for exhaust and continuous soffit vents for intake, so cold air flows under the deck. Most older homes have neither.
The roof-side backup
On a roof replacement, we install ice-and-water shield membrane at the eaves, running well inside the warm-wall line. That doesn't prevent a dam — it stops a dam from leaking even when one forms. It's the belt-and-suspenders backup to the attic work, which is why we put it on every replacement in our climate.
When You Actually Need This
- Icicles and a ridge of ice along the eaves
- Water staining a ceiling or wall during a thaw
- Recurring ice dams every winter in the same spots
- A cold room over the garage or a cathedral ceiling that leaks in winter
- You want to prevent dams before next winter
